CD4 and pulmonary fibrosis: Bronchoalveolar lavage samples from patients with pulmonary fibrosis have shown an accumulation of CD4 T cells producing IFN-γ and IL-13 (Sikkeland et al. 2021), consist with that, another study demonstrated that CD103low CD4+ tissue-resident memory cells that produced IFN-γ, IL-5, and IL-13 promoted fibrotic responses in mice chronically exposed to Aspergillus fumigatus (Ichikawa et al. 2019).